The present invention relates to a laser device and, more particularly, to a light source degradation detecting apparatus.
Various types of optical data processing apparatuses such as optical data recording/reproducing systems (so-called optical disk systems), laser printers, and optical communications systems have been commercially available in recent years. Laser sources for these systems must generate stable laser outputs. For this reason, automatic power control (APC) circuits as optical output stabilizing means are built into conventional semiconductor laser devices. Such an APC circuit feeds back a drive current to a corresponding laser source to stabilize the laser output.
However, the conventional APC circuits cannot compensate for characteristic degradation that depends on the life of a semiconductor laser. In a conventional laser device, if a predetermined laser output cannot be at a predetermined drive current, the semiconductor laser must be regarded as having reached the end of its life.
In addition, in discriminating such characteristic degradation by monitoring the drive current, a reference current and a reference light intensity must be adjusted for each semiconductor laser since the output characteristics of different semiconductor lasers are inherently different, thus resulting in an inconvenient and timeconsuming operation.
Typical recent problems in semiconductor laser life discrimination are a local change in linearity of quantization efficiency (i.e. drive current vs laser output) and an inclination of a linear gradient. The local change and the inclination cannot be detected by monitoring laser outputs generated in response to a single drive current.